The present invention relates, in general, to electronic packages, such as multi chip modules, cards, and boards and, in particular to apparatus and a method for repairing such electronic packages.
There has been a recent move to use ceramic substrates without thin films as electronic packages in high end servers. These are large ceramic multi chip module substrates with four to twenty or more chips that are connected through wiring layers in a multi layer ceramic.
Typically, there are opens and shorts among nets in ceramic multi chip module substrates that are repaired today using thin film wiring layers on top of the ceramic substrate. Without such repairs, the substrate yield would be significantly lower and this low yield would increase the cost of the multi layer chip/multi chip module substrates. Thin film repairs, unfortunately, are very expensive.
Therefore, a non-thin film repair concept and process is desired that can be used after the ceramic substrates are sintered and electrically tested for opens and shorts among signal nets. The present invention provides a concept, wiring structure, and procedure that enables post-sinter repair of multi layer ceramic signal nets in multi chip modules without using expensive thin film processes. The present invention also is applicable to other electronic packages, such as cards and boards, but the repairs of such electronic packages have different process requirements from those described in this application.
In previous repair or engineering changes of multi layer ceramic signal nets in multi chip ceramics, a metal structure was employed that enabled the defective signal net to be electrically isolated from the substrate being repaired. Typically, this metal structure included a pad connection between the chip and the substrate, a fanout line to a repair/engineering change pad, and a delete line to a via capture pad. In the case of previous all-ceramic multi chip modules, these macro-structures were outside the chip area and took up considerable top surface space, thus limiting the number of chips that could be placed on the substrate. In the case of thin film substrates, these were typically microstructures located within the cage area of the pad connection between the chip and the substrate. This latter approach was only possible with thin film substrates because of the extremely fine feature sizes required. To effect the isolation, the metal delete line of this structure was typically cut using a laser tool.
It is an objective of the present invention to provide a new and improved multi chip module substrate.
It is another objective of the present invention to provide a multi chip module substrate by which repairs can be effected in cost effective manner.
It is a further objective of the present invention to provide a new and improved method of repairing an electronic package.
It is yet another objective of the present invention to provide a method of repairing an electronic package that is cost effective.
To achieve these and other objectives, a multi chip module substrate, constructed in accordance with the present invention, includes a plurality of chip sites, each having a plurality of signal vias and a plurality of repair vias. This multi chip module also has a circuit line net having a plurality of circuit lines. Each of the circuit lines extends between and is intended to electrically connect selected signal vias. A multi chip module substrate, constructed in accordance with the present invention, further includes a repair line net having a plurality of groups of repair lines. Each repair line extends between and electrically connects a repair via of one chip site and a repair via of another chip site.
A method of repairing an electronic package, according to the present invention, includes the step of providing a multi chip module substrate that has a plurality of chip sites, each having plurality of signal vias and plurality of repair vias. This multi chip module also has a circuit line net having a plurality of circuit lines. Each circuit line extends between and is intended to electrically connect selected signal vias. This multi chip module further includes a repair line net having a plurality of groups of repair lines. Each repair line extends between and electrically connects a repair via of one chip site and a repair via of another chip site. A method of repairing an electronic package, according to the present invention, also includes the step of identifying in a circuit intended to be composed of a first signal via, a second signal via, and a circuit line extending between and intended to electrically connect the first signal via and the second signal via a defect in one of the first signal via, the second signal via, and the circuit line extending between and intended to electrically connect the first signal via and the second signal via. A method of repairing an electronic package, according to the present invention, also includes the steps of isolating the first signal via, isolating the second signal via, electrically connecting the first signal via to that repair via of the chip site having the first signal via that is connected to that repair via of the chip site having the second signal via, and electrically connecting the second signal via to that repair via of the chip site having the second signal via that is connected to that repair via of the chip site having the first signal via.